Congratulations on your new tree. I hope you will enjoy it for years to come. Of course, in the words of Pepper Provenzano, "When you plant a tree, you plant a legacy." To get the most out of your tree, and to extend the legacy it represents, you will need to help it establish roots in its new home. But be careful to avoid too much of a good thing; if the soil is already moist, adding more water can encourage fungal diseases or other problems, so always test with a finger to see if the top three inches of soil are dry before adding more water. Make sure you are digging through the mulch and checking moisture in the soil.
Container-grown trees face a challenge when first planted because the native soil tends to be different than the container soil. Moisture will quickly soak out of the root ball and into the surrounding soil, causing the tree to dry out quicker than normal. Your role at this early stage is to gradually train the roots to spread into the native soil while keeping the container soil from getting too dry too soon.
After a week or two, the tree should begin to spread into the native soil. Continue to water the root ball as needed, but every two or three days, soak the area just beyond the ball. Think of it as inviting the roots outward. It will probably take longer for the water to soak into clay, so a slow drip might be better than running water out of the hose. You can buy inexpensive soaker hoses that you can circle around the tree for this purpose, but a sprinkler will work fine in most cases if you prefer it. In sandy soils, it may be necessary to water more to allow for the increased drainage.
By the end of two months, you can generally taper off to watering twice a week. You will not need to worry as much about the original root ball, though you should still be aware of times when it is extremely dry and give it a spritz if it reaches that point. Meanwhile, you should be watering a fairly wide area around the tree. The roots that absorb water and nutrients grow outward more than downward; you really don't need to get water any deeper than 18-24 inches.
At the 3-6 month range, continue to taper off frequency and water a wider area. For most of the first year, you will probably want to stick with watering every 4-5 days. In really hot, dry weather, you still might need to water more often. After a year, the tree should be fairly well-established, and you can taper off to once a week. Continue through the second year to make sure the tree is off to a strong start. After two years, you can continue watering once a week, but if you'd like you can just go for a deep soaking once every two weeks or so. This should generally serve you well for the rest of the tree's life, though in times of severe drought even mature trees sometimes need extra water now and then.
Your tree should have started with a three-inch deep layer of hardwood mulch. This blankets the soil, helping to keep moisture from evaporating. Over time, the mulch will decay and become part of the soil. Check periodically to make sure you still have plenty of mulch; it should be a layer 3.5 inches deep, but should not be piled against the base of the tree trunk. It should cover as wide an area as possible. If you are attached to your lawn, it can coexist with your tree, but you should understand that grass is a very good competitor for water and nutrients. Giving the tree a buffer zone with no grass will allow it to thrive where a tree with grass right up to the trunk will merely survive.
As for fertiliser, we do not usually recommend it. Rather than apply a granular fertiliser that applies all of these elements, we prefer top-dressing the lawn in Spring with composted manure, which is mostly nitrogen. A thin layer (¼ to ½ inch deep) spread on the surface of your lawn will invigorate the soil ecosystem. It will also form humic acid as it decays, thus freeing up some nutrients that may be bound up with calcium in our soils due to high alkalinity. This, along with mulch, is all most trees need.
After a year or two, your young tree may benefit from pruning to develop a strong structure. Spending a little money on the tree early can save a lot of expense and stress to the tree later. For example, a quick cut to eliminate a poorly attached limb becomes a huge, expensive project if the tree is allowed to grow for several years without addressing the problem. You may want to hire an arborist to advise you or prune the tree for you when the time comes.
We hope this will help you establish a strong, healthy tree that will outlive us all. If you still have questions, learn more about basic tree care at www.yorktreeservices.co.uk
York Tree Surgeons
171a Clifford House
7-9 Clifford House,